U.S. patent application number 16/339061 was filed with the patent office on 2020-02-06 for slot rod and optical fiber cable.
This patent application is currently assigned to SUMITOMO ELECTRIC INDUSTRIES, LTD.. The applicant listed for this patent is SUMITOMO ELECTRIC INDUSTRIES, LTD.. Invention is credited to Ken TAKAHASHI, Kentaro TAKEDA.
Application Number | 20200041741 16/339061 |
Document ID | / |
Family ID | 61831066 |
Filed Date | 2020-02-06 |
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United States Patent
Application |
20200041741 |
Kind Code |
A1 |
TAKEDA; Kentaro ; et
al. |
February 6, 2020 |
SLOT ROD AND OPTICAL FIBER CABLE
Abstract
A slot rod having a plurality of grooves for storing a plurality
of optical fibers, a first layer disposed at a center of the slot
rod, a second layer provided on an outer peripheral portion of the
first layer, a third layer provided on an outer peripheral portion
of the second layer, and an outermost layer provided on an outer
peripheral portion of the third layer, and the third layer is
formed of a material having higher adhesiveness to the outermost
layer than a material in a case where the third layer is formed of
the same material as the outermost layer.
Inventors: |
TAKEDA; Kentaro;
(Yokohama-shi, Kanagawa, JP) ; TAKAHASHI; Ken;
(Yokohama-shi, Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO ELECTRIC INDUSTRIES, LTD. |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
SUMITOMO ELECTRIC INDUSTRIES,
LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
61831066 |
Appl. No.: |
16/339061 |
Filed: |
October 4, 2017 |
PCT Filed: |
October 4, 2017 |
PCT NO: |
PCT/JP2017/036114 |
371 Date: |
April 3, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/4409 20130101;
G02B 6/4434 20130101; G02B 6/44 20130101; G02B 6/4491 20130101;
G02B 6/4489 20130101; G02B 6/4408 20130101 |
International
Class: |
G02B 6/44 20060101
G02B006/44 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2016 |
JP |
2016-196561 |
Claims
1. A slot rod that includes a plurality of grooves storing a
plurality of optical fibers, the slot rod comprising: a tension
member at a center of the slot rod; a first layer adhered to the
tension member; a second layer on an outer periphery of the first
layer; a third layer on an outer periphery of the second layer; and
an outermost layer on an outer periphery of the third layer, the
outermost layer including the plurality of grooves, wherein the
third layer is formed of a material having higher adhesion to the
outermost layer than a material in a case where the third layer is
formed of the same material as the outermost layer.
2. The slot rod according to claim 1, wherein the outermost layer
is formed of polyethylene, and wherein the third layer is formed of
an ethylene-methacrylic acid copolymer.
3. The slot rod according to claim 1, wherein the outermost layer
is formed of polyethylene, and wherein the third layer is formed of
polyolefin.
4. The slot rod according to claim 1, wherein the third layer has a
radial thickness of 0.01 mm or more and 1.0 mm or less.
5. The slot rod according to claim 1, wherein an outer diameter of
the third layer is 75% or more and 99% or less of an outer diameter
at bottom portions of the plurality of grooves in the outermost
layer.
6. The slot rod according to claim 1, wherein the slot rod has an
outer diameter of 10 mm or more at top portions of ribs.
7. An optical fiber cable comprising: the slot rod according to
claim 1; a cable sheath covering outside of the slot rod; and a
plurality of optical fibers stored in the plurality of grooves in
the slot rod.
Description
TECHNICAL FIELD
[0001] The present invention relates to a slot rod and a fiber
optic cable.
[0002] This application claims priority from Japanese Patent
Application No. 2016-196561, filed on Oct. 4, 2016, the entire
subject matter of which is incorporated herein by reference.
BACKGROUND ART
[0003] A slot rod in an optical fiber cable is known. The slot rod
includes spiral grooves that store optical fibers on an outer
periphery thereof. For example, slot rods described in Patent
Documents 1 and 2 include a plurality of plastic layers around a
tensile strength member at a center, respectively.
CITATION LIST
Patent Literature
[0004] Patent Document 1: JP-UM-2-117506
[0005] Patent Document 2: JP-UM-2-117507
SUMMARY OF INVENTION
[0006] A first aspect of the present invention provides a slot rod
that includes a plurality of grooves which store a plurality of
optical fibers, the slot rod including:
[0007] a tension member at a center of the slot rod,
[0008] a first layer adhered to the tension member,
[0009] a second layer on an outer periphery of the first layer,
[0010] a third layer on an outer periphery of the second layer,
and
[0011] an outermost layer on an outer periphery of the third layer,
the outermost layer including the plurality of grooves,
[0012] in which the third layer is formed of a material having
higher adhesion to the outermost layer than a material in a case
where the third layer is formed of the same material as the
outermost layer.
[0013] A second aspect of the present invention provides an optical
fiber cable including:
[0014] the above slot rod,
[0015] a cable sheath covering outside of the slot rod, and
[0016] a plurality of optical fibers stored in the plurality of
grooves in the slot rod.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a cross-sectional view illustrating an example of
a slot rod according to an embodiment.
[0018] FIG. 2 is a cross-sectional view illustrating an example of
an optical fiber cable according to the embodiment.
DESCRIPTION OF EMBODIMENTS
Problems to be Solved by Present Disclosure
[0019] It is common in a slot rod which stores optical fibers that,
in order to ensure a groove shape and surface smoothness of the
slot rod, a material such as a polyethylene resin is extruded a
plurality of times around a tension member at a center to form the
final groove shape.
[0020] However, it is difficult to adjust an outer diameter of an
intermediate layer just inside an outermost layer when an outer
diameter of the slot rod is large, which may impair productivity.
For example, when the outer diameter of the intermediate layer is
too small relative to a diameter at bottom portions of grooves in
the outermost layer, ribs on the outermost layer may collapse
during extrusion molding due to eccentricity, and the surface
smoothness of the bottom portions of the grooves may deteriorate as
thickness of the bottom portions of the grooves in the outermost
layer increases. Meanwhile, bottom part of the grooves in the
outermost layer is thin when the outer diameter of the intermediate
layer is too large, which may deteriorate mechanical
characteristics of the slot rod. For example, adherence between the
outermost layer and the intermediate layer is weak, the ribs are
likely to be peeled off, and the ribs are likely to collapse due to
lateral pressure or shocks.
[0021] An object of the present disclosure is to provide a slot rod
and an optical fiber cable, in which rib collapse due to shocks,
lateral pressure or the like can be prevented, and a shape of
grooves and surface smoothness of bottom portions of the grooves
can be favorably ensured.
Effect of Disclosure
[0022] According to the present disclosure, rib collapse due to
shocks, lateral pressure or the like can be prevented, and the
shape of grooves and surface smoothness of bottom portions of the
grooves can be favorably ensured.
Description of Embodiments of Present Invention
[0023] An embodiment of the present invention is listed and
described.
[0024] A first aspect of the present invention provides
[0025] (1) a slot rod that includes a plurality of grooves which
store a plurality of optical fibers, the slot rod including:
[0026] a tension member at a center of the slot rod,
[0027] a first layer adhered to the tension member,
[0028] a second layer on an outer periphery of the first layer,
[0029] a third layer on an outer periphery of the second layer,
and
[0030] an outermost layer on an outer periphery of the third layer,
the outermost layer including the plurality of grooves,
[0031] in which the third layer is formed of a material having
higher adhesion to the outermost layer than a material in a case
where the third layer is formed of the same material as the
outermost layer.
[0032] According to this configuration, the third layer is adhered
to the outermost layer and is formed of a material having higher
adhesion to the outermost layer than a material in a case where the
third layer is formed of the same material as the outermost layer.
Therefore, an adhesive force between the outermost layer and the
third layer can be increased even if the outer diameter of the
third layer is increased to some extent relative to the bottom
portions of the grooves in the outermost layer. Therefore, rib
collapse due to shocks, lateral pressure or the like can be
prevented. Further, the shape of the grooves and the surface
smoothness of the bottom portions of the grooves can be favorably
ensured.
[0033] (2) The outermost layer is formed of polyethylene, and
[0034] the third layer is preferably formed of an
ethylene-methacrylic acid copolymer.
[0035] When the third layer is made of an ethylene-methacrylic acid
copolymer, the adhesion of the third layer is higher than an
adhesion of a material when the third layer is made of
polyethylene.
[0036] (3) The outermost layer is formed of polyethylene, and
[0037] the third layer is preferably formed of polyolefin.
[0038] When the third layer is made of polyolefin, the adhesion of
the third layer is higher than an adhesion of a material when the
third layer is made of polyethylene.
[0039] (4) The third layer preferably has a radial thickness of
0.01 mm or more and 1.0 mm or less.
[0040] The third layer is hardly adhesive when the radial thickness
is less than 0.01 mm, and strength of the slot rod is insufficient
when the radial thickness is larger than 1.0 mm. Therefore, the
third layer preferably has a radial thickness of 0.01 mm or more
and 1.0 mm or less.
[0041] (5) An outer diameter of the third layer is preferably 75%
or more and 99% or less of an outer diameter at bottom portions of
the plurality of grooves in the outermost layer.
[0042] When the outer diameter of the third layer is less than 75%
of the outer diameter connecting the bottom portions of the
plurality of grooves in the outermost layer, for example, the ribs
are likely to collapse during molding when, for example, the ribs
are molded by extrusion molding. When the outer diameter of the
third layer is larger than 99% of the outer diameter at the bottom
portions of the plurality of grooves in the outermost layer,
thickness of the outermost layer at the bottom portions of the
grooves is reduced, the ribs are likely to be peeled off, and the
ribs are likely to collapse due to shocks, lateral pressure or the
like. Therefore, the outer diameter of the third layer is
preferably 75% or more and 99% or less of the outer diameter at the
bottom portions of the plurality of grooves in the outermost
layer.
[0043] (6) The slot rod preferably has an outer diameter of 10 mm
or more at top portions of the ribs.
[0044] When the outer diameter is less than 10 mm, production of
the slot rod is difficult, and layers inside the outermost layer
are hardly formed. Therefore, a slot rod having an outer diameter
of 10 mm or more is preferable.
[0045] A second aspect of the present invention provides an optical
fiber cable including:
[0046] (7) the slot rod according to any one of the above (1) to
(6),
[0047] a cable sheath covering outside of the slot rod, and
[0048] a plurality of optical fibers stored in the plurality of
grooves in the slot rod.
[0049] According to this configuration, the third layer of the slot
rod in the optical fiber cable is adhered to the outermost layer
and is formed of a material having higher adhesion to the outermost
layer than an adhesion of a material in a case where the third
layer is formed of the same material as the outermost layer.
Therefore, the adhesive force between the outermost layer and the
third layer can be increased even if the outer diameter of the
third layer is increased to some extent relative to the bottom
portions of the grooves in the outermost layer. Therefore, rib
collapse due to shocks, lateral pressure or the like can be
prevented. Further, the shape of the grooves and the surface
smoothness of the bottom portions of the grooves can be favorably
ensured.
Details of Embodiments
[0050] Specific examples of a slot rod and an optical fiber cable
according to an embodiment of the present invention are described
with reference to drawings hereinafter.
[0051] The present invention is not limited to these examples but
indicated by the scope of claims, and is intended to include
meanings equivalent to the scope of claims and all modifications
within the scope.
[0052] FIG. 1 is a cross-sectional view illustrating a
configuration of a slot rod.
[0053] As illustrated in FIG. 1, a slot rod 1 includes a tension
member 10, a first layer 11, a second layer 12, a third layer 13,
and an outermost layer 14.
[0054] The tension member 10 is at a center of the slot rod 1. The
tension member 10 includes a wire rod having proof stress against
tension and compression, such as a steel wire and a
fiber-reinforced plastic wire. The tension member 10 in FIG. 1 is
stranded by a plurality of (seven) steel wires. However, the number
of steel wires may be reduced depending on, for example, a size
(outer diameter) of the slot rod 1, and one steel wire may also be
included.
[0055] The first layer 11 is outside the tension member 10 to cover
an outer periphery of the tension member 10. The first layer 11 is
formed of a material having adhesion such as an,
ethylene-methacrylic acid copolymer, and is adhered to the tension
member 10. The first layer 11 is made by extruding the
ethylene-methacrylic acid copolymer or the like around the tension
member 10.
[0056] The second layer 12 is on an outer periphery of the first
layer 11. The second layer 12 is formed of, for example, a
polyethylene resin having a high molecular density. The second
layer 12 is made by extruding the polyethylene resin or the like
around the first layer 11.
[0057] The third layer 13 is on an outer periphery of the second
layer 12. The third layer 13 is formed of a material having high
adhesion such as an ethylene-methacrylic acid copolymer and
polyolefin. The third layer 13 has a radial thickness T of 0.01 mm
or more and 1.0 mm or less. The third layer 13 is made by extruding
the ethylene-methacrylic acid copolymer, the polyolefin, or the
like around the second layer 12.
[0058] The outermost layer 14 is on an outer periphery of the third
layer 13. The outermost layer 14 is formed of, for example, a
polyethylene resin having a high molecular density. The outermost
layer 14 includes a plurality of (for example, eight) grooves 21 on
an outer periphery of the outermost layer 14. The eight grooves 21
are formed in a spiral or SZ manner in one direction along a
longitudinal direction (front-rear direction in FIG. 1) of the slot
rod 1.
[0059] The grooves 21 are partitioned by ribs 22 extending radially
from a periphery of the third layer 13. A distance from bottom
portions 23 of the grooves 21 to top portions 22a of the ribs 22 is
a depth D of the grooves 21. The grooves 21 have, for example,
substantially U-shaped cross sections, respectively. The grooves 21
preferably have a shape in which an optical fiber core wire stored
in the grooves 21 is easily rotated, respectively. The outermost
layer 14 is made by extruding the polyethylene resin or the like
around the third layer 13.
[0060] In the slot rod 1 having such elements, an outer diameter R3
of the third layer 13 is 75% or more and 99% or less of an outer
diameter R5 at the bottom portions 23 of the grooves 21 in the
outermost layer 14. The third layer 13 is formed of a material
having higher adhesion to the outermost layer 14 rather than be
formed of the same polyethylene resin as the outermost layer 14.
For example, the ethylene-methacrylic acid copolymer constituting
the third layer 13 and the polyethylene resin constituting the
outermost layer 14 have higher adhesion than between polyethylene
resins in contact with each other. Further, an outer diameter R4 at
the top portions 22a of the ribs 22 on the outermost layer 14 is 10
mm or more.
[0061] FIG. 2 is a cross-sectional view illustrating a
configuration of an optical fiber cable using the slot rod 1.
[0062] As illustrated in FIG. 2, an optical fiber cable 100
includes a wrapping tape 31 wrapped around an outer periphery of
the slot rod 1, and a cable sheath 32 covering outside of the slot
rod 1 around which the wrapping tape 31 is wrapped. Further,
optical fiber ribbons 33 formed by, for example, arranging a
plurality of optical fiber core wires in parallel are stored in the
grooves 21 in the slot rod 1.
[0063] The wrapping tape 31 is formed of, for example, a nonwoven
fabric in a tape shape, or by adhering a substrate, such as
polyethylene terephthalate, and a nonwoven fabric. The cable sheath
32 is formed of a polyethylene resin having excellent mechanical
strength or flame retardancy. The optical fiber ribbons 33 stored
in the grooves 21 may be, for example, laminated, or may be stored
as optical units in which the optical fiber ribbons are stranded
spirally in one direction.
[0064] According to the slot rod 1 and the optical fiber cable 100
configured as described above, the third layer 13 of the slot rod 1
is formed of, for example, an ethylene-methacrylic acid copolymer
or polyolefin. The outermost layer 14 is formed of, for example,
polyethylene. Accordingly, adhesion between the third layer 13
(ethylene-methacrylic acid copolymer, polyolefin) and the outermost
layer 14 (polyethylene) is higher than adhesion of the slot rod 1
having a structure in which, for example, the third layer 13 and
the outermost layer 14 are both formed of polyethylene.
[0065] When the outer diameter R3 of the third layer 13 is too
small relative to the bottom portions 23 of the grooves 21 in the
outermost layer 14, the ribs 22 may collapse during extrusion
molding due to eccentricity, and surface smoothness of the bottom
portions 23 may deteriorate as thickness of the bottom portions 23
increases. Therefore, it is desirable to make the outer diameter R3
of the third layer 13 large. However, when the outer diameter R3 is
too large, mechanical characteristics may deteriorate since the
bottom portions 23 of the grooves 21 in the outermost layer 14 are
thin. For example, the ribs 22 are likely to collapse due to
lateral pressure or shocks.
[0066] In the present embodiment, since the adhesion between the
third layer 13 and the outermost layer 14 is high, an adhesive
force between the third layer 13 and the outermost layer 14 is high
even if the outermost layer 14 at the bottom portions 23 of the
grooves 21 is made thin. Therefore, even if the outer diameter R3
of the third layer 13 is made large to avoid the above eccentricity
and deterioration of the surface smoothness of the bottom portions
23, collapse of the ribs 22 is suppressed even when lateral
pressure, shocks, or the like is applied to the slot rod 1 because
of the high adhesive force between the third layer 13 and the
outermost layer 14.
[0067] The third layer 13 has a radial thickness of 0.01 mm or more
and 1.0 mm or less. Therefore, the adhesion between third layer 13
and the outermost layer 14 is sufficiently secured by the
ethylene-methacrylic acid copolymer or polyolefin that constitutes
the third layer 13, and strength of the slot rod 1 is sufficiently
secured by this member constituting a part of the slot rod 1.
[0068] Since the outer diameter R3 of the third layer 13 is 75% or
more of the outer diameter R5 at the bottom portions 23 of the
grooves 21 in the outermost layer 14, the outermost layer 14 is
reliably held by the third layer 13, and rib collapse that may
occur during extrusion molding is further suppressed. Further,
since the outer diameter R3 is 99% or less of the outer diameter
R5, the adhesive force between the third layer 13 and the outermost
layer 14 is ensured, and peeling-off of the ribs 22 or rib collapse
due to shocks, lateral pressure or the like is prevented.
[0069] A configuration of the slot rod 1 according to the present
embodiment is preferably applied to a slot rod having the outer
diameter R4 of 10 mm or more at the top portions 22a of the ribs
22. When the outer diameter R4 is 10 mm or more, a difficulty in
manufacturing is suppressed, and the outermost layer 14 and the
first layer 11, the second layer 12, and the third layer 13 inside
the outermost layer 14 that constitute the slot rod 1 are
accurately formed.
EXAMPLES
[0070] The optical fiber cable according to the present embodiment
is described below with reference to specific examples.
[0071] Optical fiber cables, in which a material having high
adhesion to the outermost layer 14 is used as a material of the
third layer 13 in the slot rod 1 having the structure illustrated
in FIG. 1, are made experimentally (Examples 1 to 4, Example 7, and
Example 10). Further, optical fiber cables, in which the same
material as the second layer 12 and the outermost layer 14 is used
as the material of the third layer 13 in the slot rod 1 having the
structure illustrated in FIG. 1, are made experimentally (Examples
5 and 6, Examples 8 and 9, Examples 11 and 12).
Example 1
[0072] In an optical fiber cable of Example 1, an outer diameter R4
at the top portions 22a of the ribs 22 of the outermost layer 14 is
20 mm, and polyethylene having a high density is used as a material
of the outermost layer 14. An outer diameter R5 at the bottom
portions 23 of the grooves 21 is 8 mm and a depth D of the grooves
21 is 6 mm. One steel wire of 2.6 mm is used for the tension member
10, an outer diameter R1 of the first layer 11 is 3 mm, and an
ethylene-methacrylic acid copolymer (adhesive) is used as a
material of the first layer 11.
[0073] As for other conditions, as shown in Table 1, an outer
diameter R2 of the second layer 12 is 7 mm, and polyethylene having
a high density is used as a material of the second layer 12. An
outer diameter R3 of the third layer 13 is 7.5 mm, thickness T of
the third layer 13 is 0.25 mm, and an ethylene-methacrylic acid
copolymer is used as a material of the third layer 13.
[0074] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer 13 to the outer diameter R5 at the bottom portions 23
of the grooves 21 is 93.8%.
Example 2
[0075] An optical fiber cable of Example 2 is the same as the
optical fiber optical fiber cable of Example 1 except that
polyolefin is used as a material of the third layer 13 (see Table
1).
Example 3
[0076] An optical fiber cable of Example 3 is the same as the
optical fiber cable of Example 1 except that an outer diameter R2
of the second layer 12 is 5 mm, an outer diameter R3 of the third
layer 13 is 7 mm, and thickness T of the third layer 13 is 1 mm
(see Table 1).
[0077] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer 13 to the outer diameter R5 at the bottom portions 23
is 87.5%.
Example 4
[0078] In an optical fiber cable of Example 4, an outer diameter R2
of the second layer 12 is 5 mm, an outer diameter R3 of the third
layer 13 is 6 mm, and thickness T of the third layer 13 is to 0.5
mm (see Table 1).
[0079] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer 13 to the outer diameter R5 at the bottom portions 23
is 75%.
Example 5
[0080] In an optical fiber cable of Example 5, an outer diameter R4
at top portions of ribs, an outer diameter R5 at bottom portions of
grooves, depth D of the grooves, a tension member, an outer
diameter R1 of a first layer, and materials of an outermost layer
and the first layer are the same as the optical fiber cable of
Example 1.
[0081] As for other conditions, as shown in Table 1, an outer
diameter R2 of a second layer is 4 mm, and polyethylene having a
high density is used as a material of the second layer. An outer
diameter R3 of a third layer is 5 mm, and the same polyethylene
having a high density as the second layer is used as a material of
the third layer.
[0082] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer to the outer diameter R5 at the bottom portions is
62.5%.
Example 6
[0083] An optical fiber cable of Example 6 is the same as the
optical fiber cable of Example 5 except that an outer diameter R2
of a second layer is 5 mm and an outer diameter R3 of a third layer
is 7.5 mm (see Table 1).
[0084] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer to the outer diameter R5 at the bottom portions is
93.8%.
[0085] Optical fiber cables are respectively made under the
above-described conditions and mechanical properties of the optical
fiber cables are measured with results shown in Table 1.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 conditions diameter of O 7 mm O 7 mm O 5 mm O 5
mm O 4 mm O 5 mm of inner the second layers layer: R2 material of
the polyethylene polyethylene polyethylene polyethylene
polyethylene polyethylene second layer having a having a having a
having a having a having a high density high density high density
high density high density high density diameter of O 7.5 mm O 7.5
mm O 7 mm O 6 mm O 5 mm O 7.5 mm the third layer: (0.25 T) (0.25 T)
(1.0 mm T) (0.5 mm T) R3 (T) material of the ethylene- polyolefin
ethylene- ethylene- polyethylene polyethylene third layer
methacrylic acid methacrylic acid methacrylic acid having a having
a copolymer copolymer copolymer high density high density diameter
of 0.938 0.938 0.875 0.75 0.625 0.938 the third layer/diameter at
bottom portions of the grooves: R3/R5 results rib collapse No No No
No Yes No during extrusion surface Ra 0.5 Ra 0.4 Ra 0.6 Ra 0.8 Ra
2.4 Ra 0.5 roughness (Ra < 1.0) cable losses MAX MAX MAX MAX MAX
MAX (<0.25 dB/km) 0.186 0.185 0.195 0.200 0.305 0.185 dB/km
dB/km dB/km dB/km dB/km dB/km lateral .DELTA..alpha. 0.00
.DELTA..alpha. 0.00 .DELTA..alpha. 0.00 .DELTA..alpha. 0.00
.DELTA..alpha. 0.00 .DELTA..alpha. 0.25 characteristics dB/c dB/c
dB/c dB/c dB/c dB/c (.DELTA..alpha. < 0.1 dB/c)
[0086] As shown in Table 1, in the optical fiber cable of Example
5, collapse of the ribs of the outermost layer occurs during
extrusion molding due to eccentricity, since the third layer is
formed of the same material as the outermost layer, and since the
outer diameter R3 of the third layer is small relative to the outer
diameter R5 at the bottom portions of the grooves (R3/R5=62.5%).
Further, smoothness of surfaces of the grooves deteriorates (Ra=2.4
.mu.m) as thickness of the bottom portions of the grooves in the
outermost layer increases. Therefore, transmission losses of the
cable are increased (MAX 0.305 dB/km).
[0087] In the optical fiber cable of Example 6, lateral pressure
characteristics deteriorate (.DELTA..alpha. 0.25 dB/c) since the
third layer is formed of the same material as the outermost layer,
since the bottom portions of the grooves are thin because the outer
diameter R3 of the third layer is large relative to the outer
diameter R5 at the bottom portions of the grooves (R3/R5=93.85%),
and since an adhesive force of the third layer to the outermost
layer is low.
[0088] In contrast, in optical fiber cables of Examples 1 to 4, an
ethylene-methacrylic acid copolymer or polyolefin having higher
adhesion than a material (polyethylene having a high density) of
third layers in Examples 5 and 6 is used as the material of the
third layer 13. Accordingly, an adhesion force between the third
layer 13 and the outermost layer 14 is enhanced, and increased
transmission losses due to rib collapse during extrusion molding
and surface roughness of the bottom portions 23 of grooves 21 or
deterioration of mechanical properties such as rib collapse due to
lateral pressure or shocks are prevented.
Example 7
[0089] In an optical fiber cable of Example 7, an outer diameter R4
of the top portions 22a of the ribs 22 of the slot rod 1 is 30 mm.
An outer diameter R5 at the bottom portions 23 of the grooves 21 is
12 mm and depth D of the grooves 21 is 9 mm. In the tension member
10, seven steel wires of 1.4 mm are stranded for the tension member
10, and an outer diameter R1 of the first layer 11 is 6 mm.
Materials of the outermost layer 14 and the first layer 11 are the
same as in Example 1.
[0090] As for other conditions, as shown in Table 2, an outer
diameter R2 of the second layer 12 is 10 mm, and polyethylene
having a high density is used as a material of the second layer 12.
An outer diameter R3 of the third layer 13 is 10.5 mm, thickness T
of the third layer 13 is 0.25 mm, and an ethylene-methacrylic acid
copolymer is used as a material of the third layer 13.
[0091] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer 13 to the outer diameter R5 at the bottom portions 23
of the grooves 21 is 87.5%.
Example 8
[0092] In an optical fiber cable of Example 8, an outer diameter R4
at top portions of ribs, an outer diameter R5 at bottom portions of
grooves, depth D of the grooves, a tension member, an outer
diameter R1 of a first layer, and materials of an outermost layer
and the first layer are the same as the optical fiber cable of
Example 7.
[0093] As for other conditions, as shown in Table 2, an outer
diameter R2 of a second layer is 7 mm, and polyethylene having a
high density is used as a material of the second layer. An outer
diameter R3 of a third layer is 8 mm, and the same polyethylene
having a high density as the second layer is used as a material of
the third layer.
[0094] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer to the outer diameter R5 at the bottom portions is
66.7%.
Example 9
[0095] An optical fiber cable of Example 9 is the same as the
optical fiber cable of Example 8 except that an outer diameter R2
of a second layer is 9 mm and an outer diameter R3 of a third layer
is 10.5 mm (see Table 2).
[0096] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer to the outer diameter R5 at the bottom portions is
87.5%.
[0097] Optical fiber cables are respectively made under the
above-described conditions and mechanical properties of the optical
fiber cables are measured with results shown in Table 2.
TABLE-US-00002 TABLE 2 Example 7 Example 8 Example 9 conditions
diameter of the O 10.0 mm O 7.0 mm O 9.0 mm of inner second layer:
R2 layers material of the second polyethylene polyethylene
polyethylene layer having a high having a high having a high
density density density diameter of the third O 10.5 mm O 8.0 mm O
10.5 mm layer: R3 (T) (0.25 T) material of the third ethylene-
polyethylene polyethylene layer methacrylic having a high having a
high acid copolymer density density diameter of the third 0.875
0.667 0.875 layer/diameter at bottom portions of the grooves: R3/R5
results rib collapse during No Yes No extrusion surface roughness
(Ra Ra 0.6 Ra 2.8 Ra 0.6 <1.0) cable losses (<0.25 dB/km) MAX
0.186 dB/km MAX 0.315 dB/km MAX 0.186 dB/km lateral characteristics
.DELTA..alpha. 0.00 dB/c .DELTA..alpha. 0.00 dB/c .DELTA..alpha.
0.35 dB/c (.DELTA..alpha. <0.1 dB/c)
[0098] As shown in Table 2, in the optical fiber cable of Example
8, collapse of the ribs occurs during extrusion molding since the
third layer is formed of the same material as the outermost layer,
and since the outer diameter R3 of the third layer is small
relative to the outer diameter R5 of the bottom portions of the
grooves (R3/R5=66.7%). Further, smoothness of surfaces of the
grooves deteriorates (Ra=2.8 .mu.m) as thickness of the bottom
portions of the grooves increases. Therefore, transmission losses
of the cable are increased (MAX 0.315 dB/km).
[0099] In the optical fiber cable of Example 9, lateral pressure
characteristics deteriorate (.DELTA..alpha. 0.35 dB/c) since the
third layer is formed of the same material as the outermost layer,
since the bottom portions of the grooves are thin because the outer
diameter R3 of the third layer is large relative to the outer
diameter R5 at the bottom portions of the grooves (R3/R5=87.5%),
and since an adhesive force of the third layer to the outermost
layer is low.
[0100] In contrast, in the optical fiber cable of Example 7, an
ethylene-methacrylic acid copolymer having higher adhesion than a
material (polyethylene having a high density) of third layers in
Examples 8 and 9 is used as the material of the third layer 13.
Accordingly, an adhesion force between the third layer 13 and the
outermost layer 14 is enhanced, and increased transmission losses
due to rib collapse during extrusion molding and surface roughness
of the bottom portions 23 of grooves 21 or deterioration of
mechanical properties such as rib collapse due to lateral pressure
or shocks are prevented.
Example 10
[0101] In an optical fiber cable of Example 10, an outer diameter
R4 of the top portions 22a of the ribs 22 of the slot rod 1 is 10
mm. An outer diameter R5 at the bottom portions 23 of the grooves
21 is 6 mm and depth D of the grooves 21 is 2 mm. One steel wire of
1.8 mm is used for the tension member 10, and an outer diameter R1
of the first layer 11 is 2.4 mm. Materials of the outermost layer
14 and the first layer 11 are the same as in Example 1.
[0102] As for other conditions, as shown in Table 3, an outer
diameter R2 of the second layer 12 is 4.5 mm, and polyethylene
having a high density is used as a material of the second layer 12.
An outer diameter R3 of the third layer 13 is 5 mm, thickness T of
the third layer 13 is 0.25 mm, and an ethylene-methacrylic acid
copolymer is used as a material of the third layer 13.
[0103] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer 13 to the outer diameter R5 at the bottom portions 23
of the grooves 21 is 83.3%.
Example 11
[0104] In an optical fiber cable of Example 11, an outer diameter
R4 at top portions of ribs, an outer diameter R5 at bottom portions
of grooves, depth D of the grooves, a tension member, an outer
diameter R1 of a first layer, and materials of an outermost layer
and the first layer are the same as the optical fiber cable of
Example 10.
[0105] As for other conditions, as shown in Table 3, an outer
diameter R2 of a second layer is 2.6 mm, and polyethylene having a
high density is used as a material of the second layer. An outer
diameter R3 of a third layer is 4 mm, and the same polyethylene
having a high density as the second layer is used as a material of
the third layer.
[0106] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer to the outer diameter R5 at the bottom portions is
66.7%.
Example 12
[0107] An optical fiber cable of Example 12 is the same as the
optical fiber cable of Example 11 except that an outer diameter R3
of a third layer is 5 mm (see Table 3).
[0108] In this case, a ratio R3/R5 of the outer diameter R3 of the
third layer to the outer diameter R5 at the bottom portions is
83.3%.
[0109] Optical fiber cables are respectively made under the
above-described conditions and mechanical properties of the optical
fiber cables are measured with results shown in Table 3.
TABLE-US-00003 TABLE 3 Example 10 Example 11 Example 12 conditions
diameter of the O 4.5 mm O 2.6 mm O 2.6 mm of inner second layer:
R2 layers material of the second Polyethylene polyethylene
polyethylene layer having a high having a high having a high
density density density diameter of the third O 5.0 mm (0.25 T) O
4.0 mm O 5.0 mm layer: R3 (T) material of the third ethylene-
polyethylene polyethylene layer methacrylic having a high having a
high acid copolymer density density diameter of the third 0.833
0.667 0.833 layer/diameter at bottom portions of the grooves: R3/R5
results rib collapse during No Yes No extrusion surface roughness
Ra 0.5 Ra 2.8 Ra 0.5 (Ra < 1.0) cable losses (<0.25 dB/km)
MAX 0.186 dB/km MAX 0.315 dB/km MAX 0.185 dB/km lateral
characteristics .DELTA..alpha. 0.00 dB/c .DELTA..alpha. 0.00 dB/c
.DELTA..alpha. 0.25 dB/c (.DELTA..alpha. < 0.1 dB/c)
[0110] As shown in Table 3, in the optical fiber cable of Example
11, collapse of the ribs occurs during extrusion molding, since the
third layer is formed of the same material as the outermost layer,
and since the outer diameter R3 of the third layer is small
relative to the outer diameter R5 of the bottom portions of the
grooves (R3/R5=66.7%). Further, smoothness of surfaces of the
grooves deteriorates (Ra=2.8 m) as thickness of the bottom portions
of the grooves increases. Therefore, transmission losses of the
cable are increased (MAX 0.315 dB/km).
[0111] In the optical fiber cable of Example 12, lateral pressure
characteristics deteriorate (.DELTA..alpha. 0.25 dB/c) since the
third layer is formed of the same material as the outermost layer,
since the bottom portions of the grooves are thin because the outer
diameter R3 of the third layer is large relative to the outer
diameter R5 at the bottom portions of the grooves (R3/R5=83.3%),
and since an adhesive force of the third layer to the outermost
layer is low.
[0112] In contrast, in the optical fiber cable of Example 10, an
ethylene-methacrylic acid copolymer having higher adhesion than a
material (polyethylene having a high density) of third layers in
Examples 11 and 12 is used as the material of the third layer 13.
Accordingly, an adhesion force between the third layer 13 and the
outermost layer 14 is enhanced and increased transmission losses
due to rib collapse during extrusion molding and surface roughness
of the bottom portions 23 of grooves 21 or deterioration of
mechanical properties such as rib collapse due to lateral pressure
or shocks are prevented.
[0113] Although the present invention is described in detail with
reference to a particular embodiment, it is apparent to those
skilled in the art that various changes and modifications can be
made without departing from the spirit and scope of the present
invention. The numbers, positions, shapes, and the like of
components described above are not limited to the above embodiment,
and can be changed to suitable numbers, positions, shapes, and the
like during carrying out the present invention.
DESCRIPTION OF REFERENCE NUMERALS
[0114] 1 slot rod [0115] 10 tension member [0116] 11 first layer
[0117] 12 second layer [0118] 13 third layer [0119] 14 outermost
layer [0120] 21 groove [0121] 22 rib [0122] 22a top portion [0123]
23 bottom portion [0124] 32 cable sheath [0125] 100 optical fiber
cable
* * * * *